Borehole array for ranging and crosswell telemetry

ABSTRACT

An example method includes polling a plurality of reference nodes distributed along one or more reference wells. The method also includes steering a bottomhole assembly in another well based at least in part on information obtained from said polling. A related system includes a plurality of reference nodes distributed along one or more reference wells. The system also includes a bottomhole assembly in another well. The system also includes a surface controller. The surface controller polls the plurality of reference nodes to obtain position information regarding the bottomhole assembly and directs a steering module of the bottomhole assembly based on the obtained position information.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 13/056,661, filed on Jan. 30, 2011, which in turn claimspriority to PCT Pat. App. No. PCT/US2009/049470, filed on Jul. 2, 2009.The foregoing applications are hereby incorporated herein in theirentirety.

BACKGROUND

The world depends on hydrocarbons to solve many of its energy needs.Consequently, oil field operators strive to produce and sellhydrocarbons as efficiently as possible. Much of the easily obtainableoil has already been produced, so new techniques are being developed toextract less accessible hydrocarbons. One such technique issteam-assisted gravity drainage (“SAGD”) as described in U.S. Pat. No.6,257,334, “Steam-Assisted Gravity Drainage Heavy Oil Recovery Process”.SAGD uses a pair of vertically-spaced, horizontal wells less than about10 meters apart.

In operation, the upper well is used to inject steam into the formation.The steam heats the heavy oil, thereby increasing its mobility. The warmoil (and condensed steam) drains into the lower well and flows to thesurface. A throttling technique is used to keep the lower well fullyimmersed in liquid, thereby “trapping” the steam in the formation. Ifthe liquid level falls too low, the steam flows directly from the upperwell to the lower well, reducing the heating efficiency and inhibitingproduction of the heavy oil. Such a direct flow (termed a “shortcircuit”) greatly reduces the pressure gradient that drives fluid intothe lower well.

Short circuit vulnerability can be reduced by carefully maintaining theinter-well spacing, i.e., by making the wells as parallel as possible.(Points where the inter-well spacing is smaller than average providelower resistance to short circuit flows.) in the absence of precisiondrilling techniques, drillers are forced to employ larger inter-wellspacings than would otherwise be desirable, so as to reduce the effectsof inter-well spacing variations. Precision placement of neighboringwells is also important in other applications, such as collisionavoidance, infill drilling, observation well placement, coal bed methanedegasification, and wellbore intersections for well control.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the various disclosed embodiments can beobtained when the detailed description is considered in conjunction withthe drawings, in which:

FIG. 1 shows an illustrative borehole array being used to concurrentlyguide multiple bottomhole assemblies;

FIG. 2 shows an illustrative borehole array reference node;

FIG. 3 shows an illustrative environment in which a borehole array isemployed as part of a communication loop;

FIG. 4 illustrates the use of sequential nodes in a borehole array toguide multiple bottomhole assemblies;

FIG. 5 illustrates the use of multiple borehole arrays to guide multiplebottomhole assemblies;

FIG. 6 shows an illustrative communication and guidance method that canbe implemented by a reference node;

FIG. 7 shows an illustrative communication method that can beimplemented by a bottomhole assembly;

FIG. 8 shows an illustrative guidance method that can be implemented bya bottomhole assembly; and

FIG. 9 shows an illustrative communication and guidance method that canbe implemented by a surface facility.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and will herein be described in detail. Itshould be understood, however, that the drawings and detaileddescription thereto are not intended to limit the disclosed embodiments,but on the contrary, the intention is to cover all modifications,equivalents and alternatives falling within the scope of the appendedclaims.

DETAILED DESCRIPTION

The problems identified in the background are at least partly addressedby a borehole array for ranging and crosswell telemetry, along withcertain methods for employing such a borehole array. Some embodiments ofthe borehole array include a set of electrically coupled reference nodesto be distributed along the length of a reference well. Each referencenode includes a solenoid that is operated by a control unit. The controlunit employs the solenoid to generate a magnetic field for guiding abottomhole assembly in a nearby well. The control unit can further serveas a communications intermediary between the bottomhole assembly and asurface facility. With an array of such reference nodes, the bottomholeassembly can be guided in turn by subsequent reference nodes and employthe closest reference node as a communications link to the surface.Moreover, the use of multiple reference nodes offers greater precisionin determining the bottomhole assembly's position relative to thereference well. The borehole array can potentially be used to guidemultiple drilling operations at the same time.

Some embodiments of the drilling methods disclosed herein include:providing at least one reference well having an array of two or morereference nodes; electromagnetically communicating information betweenat least one of the reference nodes and a bottomhole assembly in asecond well; determining a distance or direction between the bottomholeassembly and the reference node(s); and steering the bottomhole assemblybased at least in part on said distance or direction. These operationscan be used to guide the bottomhole assembly along a path parallel tothe reference well. In some embodiments, only one of the reference nodesat a time is selected for communication with the bottomhole assembly.Where multiple wells are being drilled simultaneously, differentreference nodes can be used to communicate with different bottomholeassemblies, although it is expected that any given reference node canalso support concurrent communications with multiple bottomholeassemblies.

Other embodiments of the drilling methods disclosed herein include:providing multiple reference wells, each having at least one referencenode; drilling a target well with a bottomhole assembly; determiningdistances or directions between the bottomhole assembly and thereference nodes; and steering the bottomhole assembly based at least inpart on said distances or directions. Again, these operations can beused to direct the bottomhole assembly along a path parallel to at leastone of the reference wells. The magnetic fields produced by thedifferent reference nodes can be made distinguishable using multiplexingtechniques, e.g., frequency multiplexing, time multiplexing, and codedivision multiplexing. To determine distance and direction, thebottomhole assembly can determine a gradient of each magnetic field, oremploy one of the other distance and direction sensing techniquesinvented by Arthur F. Kuckes and disclosed in his various issuedpatents. Alternatively, the distance and direction determinations can beperformed by the reference nodes, e.g., making multi-componentmeasurements of a rotating magnetic field generated by the bottomholeassembly as taught in U.S. Pat. No. 5,589,775“Rotating Magnet forDistance and Direction Measurements From a First Borehole to a SecondBorehole”.

Turning now to the figures, FIG. 1 shows a reference well 102 having anillustrative borehole array 104 including multiple reference nodes 106coupled together via lengths of slim tubing. (The inter-node couplingscan take various alternative forms, including wireline cable or wiredpipe, either of which could be included inside a larger diameter stringof coiled or composite tubing for easy installation in the referencewell.) A well head 108 anchors the borehole array, and a cable connectsthe borehole array to a surface facility such as a logging truck 110.FIG. 1 also shows a second well 112 in the process of being drilled. Aninjector 114 pulls a coil tubing string 116 from a spool 118 and drivesit into a well. A bottomhole assembly 120 on the end of the string 116includes a mud motor and a drill bit. As drilling fluid is pumpedthrough the string, out through orifices in the drill bit, and back upthe annulus around the string, the fluid flow drives a mud motor whichturns the drill bit. The fluid flow can also drive a generator to powerdownhole electronics such as: a telemetry module, one or more sensormodules, and a steering module (discussed further below).

Also shown in FIG. 1 is a third well 122 in the process of being drilledwith a coil tubing string 124 drawn from a spool 126 and injected intothe well bore. A bottomhole assembly 128 on the end of the string 124includes various tool modules, a mud motor and a drill bit. The mudmotor is driven by the drilling fluid flow, and in turn it drives thedrill bit to extend the well bore along a desired path 129. Desired path129 is shown as running parallel to the horizontal portions of wells 102and 112 because in many cases, such as steam-assisted gravity drainage(SAGD) or coal bed degasification, it is desirable to drill a series ofclosely-spaced parallel wells. Moreover, it could be desirable to bedrilling multiple such wells at the same time.

Each of the bottomhole assemblies 120, 128 is equipped with a steeringmodule that enables the well to be extended in a desired direction. Manysuitable steering mechanisms are well known, e.g., steering vanes, “bentsub” assemblies, and rotary steerable systems. The steering mechanismconfiguration can be set and adjusted by commands from the surface,e.g., from logging truck 110 or from a driller's control panel 134.Alternatively, a downhole controller can be programmed with a desiredroute, and it can adjust the steering mechanism as needed to direct thewell along the desired path.

Each of the bottomhole assemblies can be further equipped with a sensormodule to determine the position of the bottomhole assembly relative toa desired path. The sensor module includes position sensing mechanismssuch as gyroscopes, multi-component accelerometers, and/or magnetometersto detect inertial displacement and orientations relative to gravity andthe earth's magnetic field. Moreover, the magnetometers aremulti-component magnetometers for detecting the magnetic fields emittedby the reference nodes in the borehole array, enabling the bottomholeassemblies to determine their position relative to the reference nodes,e.g., in accordance with one of the methods taught by Arthur Kuckes inU.S. Pat. Nos. 5,305,212; RE36,569; 5,823,170; and 5,589,775. In somealternative embodiments, the bottomhole assemblies emit magnetic fieldsthat can be sensed by the reference nodes to determine the relativeposition of the bottomhole assembly.

The bottomhole assemblies each further include a telemetry module thatenables the bottomhole assembly to exchange electromagnetic inter-wellcommunications with one or more of the reference nodes. Thus in FIG. 1,an arrow 130 indicates electromagnetic communications between areference node and bottomhole assembly 120, while a second arrow 132indicates electromagnetic communications between another reference nodeand bottomhole assembly 128. Since the reference nodes 106 are coupledto the surface via a wireline or wired pipe, the bottomhole assemblies120, 128 are expected to achieve a high communications bandwidth to thesurface by employing the reference nodes as communicationsintermediaries. Nevertheless, the telemetry module may also supportconventional telemetry via the drill string as a backup communicationstechnique, e.g., mud pulse telemetry, through-wall acousticcommunications, or wired drill pipe telemetry. Low frequencyelectromagnetic signaling directly to the surface is another potentialbackup communications technique.

FIG. 2 shows an illustrative reference node from a borehole array. Theillustrated node includes two end caps 201, 202 threaded on a mandrel203. Cable connectors 204 couple conductive communications lines 206 tothe reference node. A control unit 208 inside the reference nodecommunicates with the surface and optionally with other reference nodesvia the communications lines. The control unit 208 drives a winding 216on the mandrel 203 with a Magnetic Guidance Tool (MGT) signal wire 214and a ground wire 210. The control unit 208 is further configured to usewinding 216 (via a TX/RX wire 212 and ground wire 210) as atransmit/receive antenna for electromagnetic communications with abottomhole assembly. Winding 216 may have one or more tap points on itto enable the transmit signal strength to be adjusted in accordance withthe expected range to the target wellbore. (Such adjustability can beused to avoid saturating nearby receivers or to provide enough signalstrength to reach more distant receivers.) The operation of control unit208 is configured by the surface facility, e.g., whether the MGT signalis enabled and at what frequency it should be reversed, and whatcommunications channel(s) should be used for communications withbottomhole assemblies.

FIG. 3 shows another illustrative drilling environment having a boreholearray of reference nodes 302 positioned in a reference well 304. Aplatform 306 supports a drilling rig 308 having a drill string 310suspended from a top drive and a traveling block 312. A bottomholeassembly 314 at the end of the drill string 310 includes a drill bit toextend the well bore as the drill string is rotated and lowered. Aspreviously described, the bottomhole assembly includes a telemetrymodule, one or more sensor modules, and a steering module.

During the drilling process, a “mud pump” 316 circulates drilling fluiddown through the interior of drill string 310, out through orifices inthe drill bit, and upward through the annulus around the drill string.The drilling fluid transports drill cuttings to the surface andstabilizes the borehole walls.

A data acquisition/communications hub 318 is connected to the wirelinefor the borehole array in reference well 304 to exchange messages withthe reference nodes 302. Hub 318 is further connected to transducers forsending and receiving messages to the bottomhole assembly 314 via drillstring 310. Communication via the drill string 310 can be accomplishedusing mud pulse telemetry, acoustic telemetry, electromagnetic (EM)telemetry, wired drill pipe telemetry or other conventional LoggingWhile Drilling telemetry techniques. A wired or wireless link couplesthe hub 318 to a surface control system, represented by computer 320, toenable the surface control system to communicate with the bottomholeassembly 314 and the reference nodes 302.

Computer 320 executes software (represented in FIG. 3 by informationstorage media 322) to interact with a user via a display 324 and a userinput device 326. The software enables a user to view the data beinggathered by the bottomhole assembly 314 and to responsively steer thedrill bit in a desired direction. In some embodiments, the steering canbe automated by the software.

Unlike the embodiment of FIG. 1 in which the borehole array served as abidirectional communications path to the bottomhole assemblies, theembodiment of FIG. 3 employs the borehole array as a portion of aunidirectional communication loop, e.g., a loop in which commands arecommunicated from the hub 318 to the bottomhole assembly 314 via thedrill string 310, and in which data is communicated from the bottomholeassembly to the hub via a reference node in the borehole array. It isalternatively contemplated that downgoing communications would travelfrom the hub via the borehole array to the bottomhole assembly and thatupgoing communications would travel via the drill string 310. In eitherembodiment, the reference nodes enable the driller to determine theposition of the bottomhole assembly relative to the reference well.

FIG. 4 shows an illustrative series of reference nodes 402-412 in aborehole array in a reference well. As a bottomhole assembly 430 createsa nearby target well parallel to the reference well, the bottomholeassembly progresses from the coverage zone of one reference node 402 tothe next reference node 404 and thence to the next. In this manner theborehole array can provide guidance for drilling the whole length of thetarget well without requiring any re-positioning of the reference nodes.Moreover, the borehole array can provide concurrent guidance (and ahigh-bandwidth telemetry path) for multiple bottomhole assemblies.

The reference nodes in FIG. 4 have overlapping zones of coverage so thatin some positions (e.g., the position of bottomhole assembly 440)multiple reference nodes can be used to determine the relative positionof the bottomhole assembly with increased precision. In embodimentswhere the reference nodes generate magnetic fields to guide thebottomhole assembly, adjacent reference node employ a strategy to maketheir magnetic fields distinguishable by the bottomhole assembly.Conversely, in embodiments where the bottomhole assemblies generatemagnetic fields for the reference nodes to measure, the bottomholeassemblies can employ a similar strategy to enable the reference nodesto tell them apart. Suitable strategies include, without limitation,providing each node with a unique channel in a time divisionmultiplexing (TDM), frequency division multiplexing (FDM), or codedivision multiplexing (CDM) scheme. In some cases channels can bere-used when there is no danger of overlap between nodes having a commonchannel. Other potentially suitable signaling protocols employpacket-based signaling with automatic collision detection andre-transmission from nodes having unique addresses.

When a bottomhole assembly 450 drills near the edge of the coveragearea, there may be regions where the bottomhole assembly is outside theeffective navigation region, requiring the use of inertial or otherguidance techniques to steer the bottomhole assembly to the coveragezone of the next reference node. In such circumstances it may beadvantageous to provide additional communication nodes 452, 454, 456 inthe drill string to ensure at least one reference node can be reachedfor communication purposes even when the bottomhole assembly is out ofrange.

FIG. 5 shows an illustrative series of reference nodes 502-508 in afirst reference well and a second series of reference nodes 510-514 in asecond reference well. The two reference wells provide overlappingcoverage zones, enabling the bottomhole assemblies 520, 530 to navigateoff of multiple reference nodes in different wells. The overlappingcoverage zones enable greater position determination accuracy.

FIG. 6 shows an illustrative communication and guidance method that canbe implemented by a reference node. A beacon is used to implement theguidance aspect of this illustrative method, When power is supplied tothe reference node, the node activates the beacon in block 602. Thebeacon drives a solenoid to produce a magnetic field that can bedetected by a bottomhole assembly. The beacon signal is programmed tovary in a manner that enables the receiver to determine the distance anddirection to the transmitter. Because the signal pattern is known to thereceiver, the receiver can use the variations to compensate for theeffects of the earth's magnetic field. As one specific example, thebeacon can be programmed to maintain a constant signal magnitude whileperiodically reversing the signal polarity. The rate at which themagnetic field is reversed can be adjusted by a command from thesurface.

In block 604, the reference node checks for a conflict. A conflictexists if two transmitters with overlapping coverage regions aretransmitting on the same channel. To determine whether such a conflictexists, the reference node may report its assigned channel to thesurface facility (e.g., to logging truck 110) with a query as to whetherthat channel is being used by any other nodes. The surface facility canthen approve the channel or suggest an alternative channel.Alternatively, the reference node can periodically “go quiet” and listenfor other reference nodes to detect which channel they are using. Theconflict check can be skipped unless the reference node determines toomuch time has passed since the last conflict check.

If, in block 606, a conflict is determined to exist, the reference nodeacts to resolve the conflict in block 608. For the present illustrativeembodiment, such a resolution is achieved by adjusting the beaconfrequency. Once a conflict has been resolved or determined not to exist,the reference node listens in block 610 for any detectable transmissionsfrom one or more bottomhole assemblies. The signal levels of any suchtransmission are measured in block 612 and stored for possible retrievalby the surface facility. The content of any such transmission is alsomonitored for a request to open a bidirectional communications channelwith the bottomhole assembly. Upon detecting such a request, thereference node engages in a handshaking operation to determine theprotocol and sets up transmit and receive queues.

In block 614, the reference node checks for a command from the surfacefacility. Commands that can be received from the surface facility areexpected to include: a command to read signal levels of any detectedbottomhole assembly transmission; commands to transmit a message over anopen channel; and commands to change the configuration of the referencenode, including enabling or disabling the beacon.

In block 616, the reference node carries out any such received commands.For example, the reference node can transmit the measured signal levelsof the detected transmissions. If the surface facility provides amessage to be sent to a bottomhole assembly with which the referencenode has an open channel, the message is placed in the transmit queue.

In block 618, the reference node checks for open communicationschannels. If any are open, the reference node checks the correspondingmessage queues in block 620. Any messages in the transmit queue are sentto the bottomhole assembly and any messages in the receive queue aresent to the surface facility. Such message exchanges can be initiated bythe reference node control process and left to be carried out byparallel threads or independent hardware in the reference node. Thecontrol process loops back to block 604.

FIG. 7 shows an illustrative communication method that can beimplemented by a bottomhole assembly. Once the method is initiated, thetelemetry module in bottomhole assembly begins searching for referencenode beacons in block 702. Block 704 checks to determine if a beacon hasbeen found, and if not, the telemetry module loops back to block 702.Once one or more beacons have been found, the telemetry module reachesblock 706, where the telemetry module selects the source of thestrongest beacon as a communications node. In block 708, the telemetrymodule initiates a handshaking operation with the selected referencenode to open a bi-directional communications channel.

In block 710, the telemetry module performs a message exchange with thereference node. The message exchange includes transmitting messagepackets with any data that the bottomhole assembly is configured toacquire and transmit to the surface facility. Such data can includeinformation regarding the position and velocity of the bottomholeassembly, formation properties that have been logged, and performancecharacteristics of the bottomhole assembly.

The message exchange further includes receiving any commands that mighthave been sent by the surface facility. If any such commands arereceived, the receipt of such commands is optionally acknowledged inblock 712. In some embodiments, the acknowledgement is sent via theelectromagnetic communication link to the reference node, while in otherembodiments, the acknowledgement is communicated via the drill string.

In block 714, the telemetry module checks the receive queue to determineif any of the received messages include a command from the surfacefacility. If so, the telemetry module carries out the command in block716. Such commands can include commands to change the configuration oroperating parameters of the bottomhole assembly. Other illustrativecommands are commands to have selected data or parameter valuestransmitted to the surface facility.

In block 718, the telemetry module checks the quality of theelectromagnetic communications link. If the channel is degrading (e.g.,the signal-to-noise ratio is below a given threshold, or too many symbolerrors are detected), the telemetry module closes the channel and loopsback to block 702. Otherwise the telemetry module loops back to block710 to perform another message exchange.

FIG. 8 shows an illustrative guidance method that can be implemented bya bottomhole assembly. This guidance method runs concurrently with thecommunication method described above, and may be implemented within thetelemetry module or separately in the sensor module of the bottomholeassembly. In block 802, the bottomhole assembly searches for referencenode beacons. In block 804, a check is made to determine whether atleast one beacon has been found, and if not, the method loops back toblock 802.

Once at least one beacon has been detected, the bottomhole assemblydetermines the distances and directions to each of the detectablebeacons in block 806. Suitable methods for determining distance anddirection are disclosed by Arthur Kuckes in U.S. Pat. Nos. 5,305,212;RE36,569; 5,823,170; and 5,589,775. The methods taught by Kuckes aredescribed in terms of a single reference node, but they are adaptablefor use with multiple reference nodes by providing each reference node(or other magnetic field generator) with a distinctive signature thatenables individual measurement of each magnetic field. As one example,the reference nodes can be enabled only one at a time and cycled in apredetermined sequence. In an alternative embodiment, each of thereference nodes reverses its magnetic field periodically with afrequency that is different from any other reference node. As yetanother possible embodiment, the magnetic field generated by eachreference node is modulated with a code that is orthogonal to the codesused by other nodes.

Whichever technique is chosen for making the magnetic fields distinctiveallows the bottomhole assemblies to determine and monitor the gradientof the magnetic field. Given the change in gradient as a function ofbottomhole assembly position, the distance and direction to the sourceof the magnetic field can be estimated. However, other methods fordistance and direction determination can alternatively be employed,including monitoring of a rotating magnetic field, monitoring traveltimes, and/or triangulating relative to multiple magnetic field sources.

In block 808, the bottomhole assembly determines its position relativeto the reference boreholes based at least in part on the distances anddirections to the reference nodes. The bottomhole assembly can alsoemploy displacement measurements and knowledge of the reference boreholegeometry and positions of the reference nodes within the reference well.This information can be transmitted to the surface facility or, inoptional block 810, the information can be provided to the steeringmodule for use in keeping the bottomhole assembly on its programmedtrack. The method repeats as the bottomhole assembly moves, enabling thebottomhole assembly to track its position.

FIG. 9 shows an illustrative communication and guidance method that canbe implemented by a surface-based controller of the downhole activity.Beginning in block 902, the controller polls each of the reference nodesin the one or more borehole arrays, obtaining signal level measurementsand any messages directed to the surface facility. Based on the gatheredinformation, along with any other available information (such as lengthof the drill pipe in the hole), the controller determines the positionof each bottomhole assembly in block 904. These positions can beexpressed in absolute terms, but in at least some embodiments, thesepositions are expressed relative to one or more of the reference wells.

In block 906 the controller selects, for each bottomhole assembly, areference node to serve as a communications intermediary with thatbottomhole assembly. If the bottomhole assembly is not currently in acoverage zone, the selected reference node will be the next referencenode that will come within range of the bottomhole assembly. On theother hand, if the bottomhole assembly is currently in a coverage zone,the selected reference node will usually be the node having thestrongest signal or otherwise offering the highest channel capacity. Inselecting a reference node, the controller may take into accountpotential interference from other bottomhole assemblies and previousperformances of the candidate nodes.

Note that in some embodiments, the bottomhole assemblies select thereference nodes to be used as communications intermediaries. In suchembodiments, the controller adopt those selections by detecting whichreference nodes have open channels. Alternatively, the controller candisable unselected reference nodes and/or command the bottomholeassembly to switch between reference nodes.

In block 908, the controller checks for open communications channels. Ifnone have yet been opened, the controller loops back to block 902.Otherwise, in block 910, the controller exchanges messages with thebottomhole assemblies to gather data and monitor their positions andprogress. In some embodiments, the controller sends commands to thebottomhole assemblies to steer them along desired paths. In otherembodiments, each bottomhole assembly steers itself along a programmedpath, and the controller only intervenes to change the programmed pathif something unexpected occurs.

In block 912, the controller determines whether a channel has beenclosed or there is some other reason for changing a selected referencenode. If not, the controller loops back to block 910. Otherwise thecontroller loops back to block 902.

Numerous variations and modifications will be apparent to those ofordinary skill in the art once the above disclosure is fullyappreciated. It is intended that the following claims be interpreted toembrace all such variations and modifications. As one example, ratherthan having the bottomhole assembly measure magnetic fields generated byreference nodes, alternative embodiments have the reference nodesmeasuring magnetic fields generated by the bottomhole assemblies. Thereference nodes can individually or cooperatively determine the relativeposition of each bottomhole assembly and communicate it or othersteering information to the bottomhole assembly via the electromagneticcommunications link.

What is claimed is:
 1. A method that comprises: emitting electromagneticbeacons by at least some of a plurality of electromagnetic referencenodes distributed along one or more reference wells and wired to asurface controller; storing, by said at least some of the plurality ofelectromagnetic reference nodes, position information comprising atleast one type of data consisting of distance and direction of abottomhole assembly in another well wherein each of the plurality ofelectromagnetic reference nodes includes a data queue responsive tobeing polled, and wherein the bottomhole assembly is configured todetermine the position information relative to an emitted beacon fromone of the plurality of reference nodes, to open a communication channelwith said one of the plurality of reference nodes, and to provide theposition information to a corresponding data queue; polling said atleast some of the plurality of electromagnetic reference nodesdistributed along the one or more reference wells; conveying theposition information stored by said at least some of the plurality ofelectromagnetic reference nodes to the surface controller in response tosaid polling; and steering the bottomhole assembly in the other wellbased at least in part on triangulating a position of the bottomholeassembly relative to two or more of the plurality of electromagneticreference nodes using respective emitted beacons from the two or more ofthe plurality of electromagnetic reference nodes and the positioninformation obtained from said polling.
 2. The method of claim 1,further comprising selecting said one of the plurality of referencenodes to be a communications intermediary between the surface controllerand the bottomhole assembly.
 3. The method of claim 2, wherein saidselecting comprises identifying said one of the plurality of referencenodes as closest to the bottomhole assembly.
 4. The method of claim 2,wherein said selecting comprises detecting which of the plurality ofreference nodes has an open communication channel with the bottomholeassembly.
 5. The method of claim 2, wherein said selecting accounts forany channel conflicts and any interference from at least one otherbottomhole assembly within range of said one of the plurality ofreference nodes.
 6. The method of claim 2, further comprising performinga handshaking operation between the selected reference node of said oneof the plurality of reference nodes and the bottomhole assembly.
 7. Themethod of claim 1, further comprising: detecting, by the bottomholeassembly, a beacon corresponding to said one of the plurality ofreference nodes; opening a communication channel between the bottomholeassembly and said one of the plurality of reference nodes associatedwith the beacon; and performing a message exchange between thebottomhole assembly and said one of the plurality of reference nodes viathe opened communication channel.
 8. The method of claim 1, furthercomprising: detecting, by the bottomhole assembly, a beaconcorresponding to said one of the plurality of reference nodes;determining, by the bottomhole assembly, the distance and direction tothe beacon; and performing, by the bottomhole assembly, at least oneaction selected from the group consisting of providing the positioninformation related to the determined distance and direction to said oneof the plurality of reference nodes, and using the position informationto direct a steering module.
 9. The method of claim 1, furthercomprising switching said one of the plurality of reference nodesbetween a beacon enabled configuration and a beacon disabledconfiguration.
 10. The method of claim 1, further comprising: storing,by said one of the plurality of reference nodes, a message from thebottomhole assembly; and conveying the message in response to saidpolling, wherein the message includes information regarding at least oneof a bottomhole assembly velocity, bottomhole assembly performancecharacteristics, and logged formation properties.
 11. The method ofclaim 1, further comprising modulating timing or frequency attributes ofbeacons emitted by the plurality of reference nodes to enable said eachreference node of the plurality of reference nodes to be associated witha distinct beacon.
 12. A system that comprises: a plurality ofelectromagnetic reference nodes distributed along one or more referencewells, wherein at least some of the plurality of electromagneticreference nodes emit a beacon; a bottomhole assembly in another well,wherein each of the plurality of electromagnetic reference nodesincludes a data queue responsive to being polled, and wherein thebottomhole assembly is configured to determine position informationrelative to aft the emitted beacon from said at least some of theplurality of electromagnetic reference nodes, to open a communicationchannel with one of the plurality of reference nodes, and to provide theposition information to a corresponding data queue; and a surfacecontroller wired to the plurality of electromagnetic reference nodes,wherein the surface controller polls the plurality of electromagneticreference nodes to obtain the position information regarding thebottomhole assembly from respective data queues and directs a steeringmodule of the bottomhole assembly based on triangulating a position ofthe bottomhole assembly relative to two or more of the plurality ofelectromagnetic reference nodes using respective beacons of the two ormore of the plurality of electromagnetic reference nodes and theobtained position information.
 13. The system of claim 12, wherein thesurface controller selects said one of the plurality of reference nodesto be a communications intermediary between the surface controller andthe bottomhole assembly.
 14. The system of claim 13, wherein the surfacecontroller selects a reference node identified as closest to thebottomhole assembly as the communications intermediary.
 15. The systemof claim 13, wherein the surface controller selects a reference nodeidentified as having an open communication channel with the bottomholeassembly as the communications intermediary.
 16. The system of claim 13,wherein the surface controller directs said one of the plurality ofreference nodes to switch between a beacon enabled configuration and abeacon disabled configuration.
 17. The system of claim 12, wherein saideach of the plurality of reference nodes includes a data queueresponsive to being polled, wherein the bottomhole assembly isconfigured to open a communication channel with said one of theplurality of reference nodes and to provide a message to a correspondingdata queue, wherein the message includes at least one of a bottomholeassembly velocity, logged formation properties, and bottomhole assemblyperformance characteristics.
 18. The system of claim 12, wherein theplurality of reference nodes couple to the surface controller via awireline cable or wired pipe.